Bearing pressure

Bearing pressure is a particular case of contact mechanics often occurring in cases where a convex surface (male cylinder or sphere) contacts a concave surface (female cylinder or sphere: bore or hemispherical cup). Excessive contact pressure can lead to a typical bearing failure such as a plastic deformation similar to peening. This problem is also referred to as bearing resistance. A contact between a male part (convex) and a female part (concave) is considered when the radii of curvature are close to one another. There is no tightening and the joint slides with no friction therefore, the contact forces are normal to the tangent of the contact surface. Moreover, bearing pressure is restricted to the case where the charge can be described by a radial force pointing towards the center of the joint. In the case of a revolute joint or of a hinge joint, there is a contact between a male cylinder and a female cylinder. The complexity depends on the situation, and three cases are distinguished: the clearance is negligible: a) the parts are rigid bodies, b) the parts are elastic bodies; c) the clearance cannot be ignored and the parts are elastic bodies. By "negligible clearance", H7/g6 fit is typically meant. The axes of the cylinders are along the z-axis, and two external forces apply to the male cylinder: a force along the y-axis, the load; the action of the bore (contact pressure). The main concern is the contact pressure with the bore, which is uniformly distributed along the z-axis. Notation: D is the nominal diameter of both male and female cylinders; L the guiding length. In this first modeling, the pressure is uniform. It is equal to: If it is considered that the parts deform elastically, then the contact pressure is no longer uniform and transforms to a sinusoidal repartition: P(θ) = Pmax⋅cos θ with This is a particular case of the following section (θ0 = π/2). The maximum pressure is 4/π ≃ 1.27 times bigger than the case of uniform pressure.